How do I identify Simonkolleite?

Simonkolleite can be identified by its hardness of 1.5 on the Mohs scale, Colourless color. Look for these key characteristics when examining specimens.

What color is Simonkolleite?

Simonkolleite typically appears in Colourless. Color can vary depending on impurities and formation conditions.

How hard is Simonkolleite?

Simonkolleite has a hardness of 1.5 on the Mohs scale. This makes it a soft mineral that can be scratched easily.

Simonkolleite

A variety of Minerals

What is Simonkolleite?

Zinc chloride hydroxide monohydrate is a zinc hydroxy compound with chemical formula Zn5(OH)8Cl2·H2O. It is often referred to as tetrabasic zinc chloride (TBZC), basic zinc chloride, zinc hydroxychloride, or zinc oxychloride. It is a colorless crystalline solid insoluble in water. Its naturally occurring form, simonkolleite, has been shown to be a desirable nutritional supplement for animals.

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Simonkolleite Localities Map

See where Simonkolleite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.

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North ZoneCentral RidgeSouth Basin

Key Characteristics

Characteristics of Simonkolleite

Simonkolleite is colorless, forms tabular hexagonal crystal up to 1 mm in diameter, and has perfect cleavage parallel to (001). Thermal stability studies have shown that simonkolleite decomposes to ZnO at several stages upon heating (eq. 1-3). The decomposition starts with loss of a single mole of the lattice water. Further dehydration at 165 ~ 210 °C produces a mixture of ZnO and an intermediate Zn(OH)Cl. At 210 ~ 300 °C, the intermediate Zn(OH)Cl decomposes to ZnO and ZnCl2. At higher temperature, volatilization of zinc chloride occurs, leaving a final residue of zinc oxide. The dehydrated mixture (Zn(OH)Cl and ZnO) is easily rehydrated and converted back to simonkolleite upon exposure to cool moist air (eq. 4). Simonkolleite is virtually insoluble in water and organic solvents, soluble in mineral acids yielding the corresponding zinc salts (eq. 5), soluble in ammonia, amine and EDTA solutions under complex formation. It can easily be converted to zinc hydroxide by reacting with sodium hydroxide (eq. 6). Its pH in water is 6.9 measured by EPA method SW846-9045.

Composition of Simonkolleite

Simonkolleite is rhombohedral, space group R3m. There are two crystallographically distinct zinc sites in Simonkolleite, both of which are fully occupied by zinc. The Zn(1) site is coordinated by six hydroxyl (OH) groups in an octahedral geometry [Zn(OH)6]. The Zn(2) site is coordinated by three OH groups, and one Cl atom in a tetrahedral geometry [Zn(OH)3Cl]. The [Zn(OH)6] octahedra form an edge-sharing dioctahedral sheet similar to that observed in dioctahedral micas. On each site of the vacant octahedron, a [Zn(OH)3Cl] tetrahedron is attached to three anions of the sheet and points away from the sheet. Intercalated between adjacent sheets are interstitial water (H2O) groups. The sheets are held together by hydrogen bonding from OH groups of one sheet to Cl anions of adjacent sheets, and to interstitial H2O groups. The [Zn(OH)6] octahedra have four long equatorial bonds (at 2.157 Å) and two short apical bonds (at 2.066 Å). This apical shortening is a result of the bond-valence requirements of the coordinating OH groups and the connectivity of polyhedra in the structure. The equatorial OH groups [O(1)H] are coordinated by two Zn(1) cations and one Zn(2) cation, whereas the apical OH groups [O(2)H] are coordinated by three Zn(1) cations. As Zn(1) is six-coordinated and Zn(2) is four-coordinated, the local bond-valence requirements require the Zn(1)-O(1) bonds to be considerably longer than the Zn(1)-O(2) bonds. The [Zn(OH)3Cl] tetrahedron has three short Zn(2)-O(1) bonds (at 1.950 Å) and one long Zn(2)-Cl bond (2.312 Å) (Figure 1).